The investigation of influence of localized states on a-Si:H p-i-n photodiode transient response to blue light impulse with blue light optical bias

Abstract

The series of experiments measuring the transient response of a-Si:H pin photodiode to light impulses superimposed to constant light (optical bias dependence of modulated photocurrent method — OBMPC) of the same wavelength (430 nm) and various reverse voltages on photodiode was performed in order to characterize localized states of the energy gap of amorphous silicon and their influence on photocurrent degradation. The responses were analyzed as a sum of decaying exponential functions using the least squares method and a generalized Fosse's algorithm. This type of response is typical for independent relaxation processes running at the same time. Experiments and subsequent data processing illustrate feasibility of the method and results for the transient response of a-Si:H pin photodiode. The results strongly suggest two energy levels between 0.32 eV and 0.45 eV. These results were obtained applying the optical ac blue and dc blue bias light in a low frequency regime.